The 2012 328i's biggest change is its engine. It is smaller and more efficient than in the previous model, delivering better fuel economy in addition to more horsepower and torque.

The styling is just this side of conservative, buttoned-up but not straight-jacketed. Away from the executive parking lot, it makes almost any commute a good time. No other model in BMW’s line is more important. Like Porsche’s 911, it defines the brand.

This winter we get a new, sixth generation of the four-door fun-maker. (The coupe and M3 versions won’t change for another two model years.) As usual, the 3 comes in two flavors, the 335i and the less-expensive 328i. About 70 percent of sales are the latter. The 2012 models start at $43,295 and $35,795.

After two days testing both models around central California and on a closed racetrack, I found myself thinking “less is more,” and “sometimes things are overrated for a reason.”

The 3 Series earns its reputation yet again. It’s the best stew of technology, driving pleasure and comfort I can think of in its class. (Which BMW calls a “premium compact sports sedan,” but doesn’t feel compact.) This time, less really is more. I prefer the 328i over the 335i.

This is because the 328i loses its longtime six-cylinder engine in favor of a more economical four-cylinder. The smaller powerplant transforms the platform, making it feel younger, less conservative and more lively. At 240 horsepower, it has 10 more horses than the outgoing 328i, and an extra 55 pound-feet of torque, which reaches its peak 1,500 rpm earlier. Basically it’s got more get-up-and-go, right off the line.

Keep an eye on the tachometer. While cruising, it hovers between 2,000 and 3,000 rpm, but pounce on the accelerator and there’s a tiny pause, then it slingshots to 5,000 rpm on its way to the 7,000 redline. Like Pop Rocks in your mouth, just add soda for the fizzy explosion.

It gets gas mileage of 24 city, 36 highway for the four-cylinder with an automatic transmission. Stop and consider that a moment: 36 mpg highway for a car this fun. This European. It feels like a guilty pleasure but isn’t.

The transmission has been upgraded to eight speeds, and it crackles quickly through the lower gears to ensure snappy starts, then slides to eighth for the best gas savings. BMW says the new 328i should see an improvement of 8 mpg on the highway.

Some buyers might sniff at a four-cylinder BMW, suggesting that it simply can’t be refined as it should. And to be sure, the 328i’s engine has a burr that’s less than sonorous. Those standing outside the car will notice it more than those inside.

For those purists, there’s the turbo-charged, six-cylinder 335i. The engine gets 300 horsepower and 300 pound-feet of torque and is fantastic in almost every way. The heavier 335i gets 23 city, 33 highway, with the automatic transmission.

Very few stock 3 Series will find themselves on the racetrack, but the opportunity to drive both models full-out was instructive. The 335i’s extra power hurls it out of corners. My top speed on a straightaway was 112 mph versus 108 mph with the 328i. But the lighter car’s engine is located fully behind the front axles, giving it better balance. It playfully dances into corners.

Ultimately, I was quicker around the track in the 328i, if only slightly. Less is faster.

Visually, the biggest difference between the new generation 3 Series is the front. The headlights extend all the way inward toward the center, touching the double-kidney grille. Slightly more modern, but it takes away from the distinctiveness of that signature BMW face.

BMW has simplified the ordering process by giving buyers three trim levels: sport, luxury and modern. They get slightly different finishes on the front grills and specific interior treatments.

Luxury is heavy on wood, sport on red stitching. The interior of the last generation was spartan and unsatisfying. It seemed to suggest you’re better keep your eyes on the road.